SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '42f47b18752f633b8a801558a140077819f8afba49dea50928430e8e1fd2e29b' 
  AND token = 'qIqh3gbOGy1sAL+1Ck40+FJLZSY6djyiHmMpHs6ryWw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}